1. Technical Field
The invention relates to a three-dimensional measurement system and method thereof. More particularly, the invention relates to an optical configuration within a three-dimensional measurement system.
2. Description of Related Art
With the shrinking of the dimensions of electronic components in recent years, some automated high-precision testing equipment has been developed for performing detection of the appearance, circuitry connection and alignment relationship of electronic components. For example, the Solder Paste Inspection (SPI) machine has been widely used in production lines for performing precise measurements with respect to the size of solder paste on substrates, and has become a necessary tool for controlling the manufacturing process of printed circuit boards.
Among the various methods for measuring the three-dimensional shape of a DUT (device under test), there is one common measuring method based on Fringe pattern projection in the prior art. This measuring method involves utilizing a projector module to project an equal-spaced-multi-line pattern onto a DUT, and then reconstructing a three-dimensional surface profile of the DUT from 3˜12 phase-shift images of the DUT.
In response to industry demands, technologies related to Solder Paste Inspection (SPI) are being improved continuously. For example, some traditional solutions sequentially project plural sets of Fringe Pattern onto a DUT that is being measured along different projective angles, and correspondingly obtain a three-dimensional shape from the reflective images of the DUT. These solutions may achieve faster speed and higher precision by utilizing plural sets of fringe pattern projections along different projective angles.
Typically, the multiple sets of fringe pattern projections along different projection angles are generated either by the same amount of multiple projector modules implemented together, or a single projector module implemented along with an optical path switching structure.
Among the above two techniques, implementing multiple projector modules at different angles is an straight forward solution for generating fringe pattern projections along different incident angles. However, this traditional solution requires one three-dimensional measurement apparatus to include multiple projector modules, each of which includes at least a light source, a grating unit and projective lenses. Therefore, this traditional solution leads to very high manufacturing cost, and huge space in the apparatus.
The other traditional approach involving the use of one projector module along with an optical path switching mechanism may be used to solve the aforesaid problems.
FIG. 1 is a schematic diagram illustrating a traditional three-dimensional measurement system 100 and an optical path switching structure thereof.
As shown in FIG. 1, a light source 120 within a projector module of the traditional three-dimensional measurement system 100 generates a light beam L0. The light beam L0 is projected onto a switchable reflective mirror 140. The switchable reflective mirror 140 can be switched to selected positions. As an example, when the switchable reflective mirror 140 is switched to position P1, the light beam L0 is then reflected along the optical path L1 to the left, and subsequently onto a DUT (device under test) 200. As another example, when the switchable reflective mirror 140 switched to position P2, the light beam L0 is reflected along the optical path L2 to the right, and subsequently onto the DUT 200.
As shown in FIG. 2, which is an isometric view of the switchable reflective mirror 140 shown in FIG. 1, the switchable reflective mirror 140 in this solution is an optical element on a mechanical base. However, the switching vibrations of both optical and mechanical parts will cause the fluctuation of the optical path. Therefore, this solution will result in an excessive inaccurate measurement unexpectedly
Reference is now made to FIG. 3 and FIG. 4. FIG. 3 is a schematic diagram illustrating another known three-dimensional measurement system 100 and an optical path switching mechanism 142 thereof. FIG. 4 is an isometric view of the optical path switching mechanism 142 shown in FIG. 3.
As shown in FIG. 3 and FIG. 4, the optical path switching mechanism 142 has a sliding prism 144. The optical path is switched by changing the position of the sliding prism 144. As an example, when the sliding prism 144 slides to position P1 along the guiding slit, a light beam L0 is then reflected along the optical path L1 to the left, and subsequently onto a DUT (device under test) 200. As another example, when the sliding prism 144 slides to the position P2 along the guiding slit thereto, the light beam L0 is reflected along the optical path L2 to the right, and subsequently onto the DUT 200. With this configuration, there are the same issues on the optical path switching mechanism 142 as well. Therefore, this solution will result in the same excessive inaccurate measurement therewith.